1. Field of the Invention
The present invention is directed to a system of controlling aircraft and ground traffic at and near airports.
2. Description of the Related Art
As airport and air traffic congestion become recognized as seriously threatening the future of our aviation transportation system, it is clear that both safety and capacity will receive equal recognition as primarily system design criteria. Runway incursions, defined as any occurrence at an airport involving an aircraft, vehicle, persons, or object on the ground that creates a collision hazard or results in loss of separation with an aircraft taking off, intending to take off, landing or intending to land. It can be said that runway incursions directly impact airport capacity and airport safety.
The problem of reduced airport capacity and reduced airport safety stems primarily from the fact that a majority of airport operations are manually controlled by the control towers, the cockpits, and the radar rooms. There exist a number of human factor considerations which impact airport capacity, such as variable airport controller capability, variable landing intervals, variable pilot response, variable pilot procedures, pilot response in landing on a crossing runway and runway design.
Regarding variable airport controller capability, controllers have different capabilities in handling landings and takeoffs. This difference is more noticeable at airports which experience high demand rates and complex flight situations. With variable landing intervals, differences in personnel capability and procedures lead to significant variation in intervals between landings. Therefore, each landing interval must be appraised on an individual basis, and the opportunity to permit a takeoff between two landings is unique to the controller.
With regard to variable pilot response, studies show that pilots react differently to instructions from the controller. Consequently, any perceived delay to takeoff (controllers will typically associate a quick or delayed response to certain types of aircraft and airlines) must be considered by the controller in any decision to permit a takeoff between landings, or require a hold until a later time. In terms of variable pilot procedures, procedures for initiating takeoff vary between airlines, and thus, the controller must react to a perceived slow reaction or delay by a pilot. Studies further show that, even though the controller may authorize an aircraft for takeoff, pilots are often reluctant to initiate takeoff before an inbound aircraft has traversed the intersection. The unwillingness to initiate takeoff is directly related to the distance between takeoff point and the intersection, and either decreases safety margins or decreases airport capacity.
Moreover, adverse weather, reduced visibility, radio frequency congestion, language ambiguities, and other real-world occurrences add another dimension to the aircraft control problem reducing control effectiveness below the desired level of excellence.
In response to the need to enhance airport safety, there has been a call to implement automated airport control systems. However, these control systems are disadvantageous because they focus primarily on the issue of runway incursion, and thus, are designed to alert the airport controllers when to stop or halt aircraft and/or ground vehicles from entering an active runway. In other words, conventional automated airport control systems indirectly inform the aircraft pilot only when to xe2x80x9cstopxe2x80x9d or halt ground-based based aircraft and/or vehicles. Secondly, the control systems are disadvantageous since they fail to focus on enhancing both airport safety and airport capacity.
In view of the foregoing, it is an object of the invention to provide an airport control system for enhancing airport capacity and airport safety.
It is another object of the invention to provide an airport control system for reducing airport runway incursions.
It is further object of the invention to provide an automated airport control system for controlling aircraft and ground traffic at an airport.
It is still another object of the invention to provide an automated airport control system adapted to forecast an optimum time for an aircraft to initiate a takeoff in order to be safely sequenced between successive landings on either crossing/intersecting runways or on the same/single runway.
It is yet another object of the invention to provide an automated airport control system that permits an aircraft takeoff position at an acute angle relative to the runway.
These, as well as other objects are achieved in providing an airport control system which includes a sensing mechanism for sensing a plurality of target conditions, a processing mechanism which receives the target conditions input from the sensing mechanism, and a plurality of visual displays in electronic communication with the processing mechanism which alerts a ground pilot when to xe2x80x9cstopxe2x80x9d or halt the aircraft in addition to alerting the pilot when to xe2x80x9cgoxe2x80x9d or proceed on the taxiway in response to an electronic signal received from the processing mechanism. Hence, the airport control system in accordance with the present invention is capable of tracking inbound flights at an airport and forecast when each arrival will touchdown and/or cross intersecting runways.
In accordance with the present invention, the sensing mechanism is adapted to track a plurality of target conditions, such as at least one of the following: the position and velocity of inbound aircraft, the time from start of roll to the time of clearing an intersection of the aircraft awaiting takeoff, aircraft configuration (such as aircraft model), atmospheric conditions (i.e., temperature, visibility conditions, wake turbulence conditions, wind direction and velocity, barometric pressure, etc.), runways in use, and the distance from holding area to the intersecting runway. Other target conditions may also be included, such as mode of airport usage, i.e., whether the airports are subject to either takeoffs only, landings only, or interleaved takeoff and landing.
Preferably, land-based surveillance systems, such as radar, or air-based systems including GPS or other on-board navigation systems are provided to sense the target conditions. The system may also forecast, during a takeoff sequence, the time it takes for an aircraft to cross through an intersection. Information for this forecast may be derived from manufacturer performance data for the runway in combination with corrections for wind and temperature for the specific aircraft. Beacon associated techniques, such as the ATCRBS Beacon (ARTS), Bendix trilateration technique, Westinghouse(trademark) interferometer and the MIT Precision Approach and Landing Monitor (PALM) systems may be employed to determine the position and velocity of approaching or inbound aircraft. The time from start of roll to the time of clearing an intersection of the aircraft awaiting takeoff may be determined from the type of aircraft, temperature and wind information. The type of aircraft is typically stored in flight strip information, which may be accessed electronically using a known system. In addition, the time from touchdown until the landing has exited the runway will be determined by the system, preferably by utilizing a manual tower position.
The sensed target conditions will be input into the processing mechanism, such as a computer or the like and includes an electronic controller. The computer preferably includes software capable of calculating the optimum time in which all aircraft awaiting departure may initiate a takeoff sequence based upon the sensed target conditions. The computer preferably includes a storage device adapted to retrievably store therein electronic files of information (i.e., target conditions) used in calculating the optimum take off window. Using a maximum likelihood filter, the computer filters the target condition to output a velocity for each aircraft on final approach to landing and place them in landing order. Using this information, the computer would then calculate the time that the next approaching aircraft is expected to cross the intersection (i.e., of intersecting runways) and, taking into account the estimated roll time of the holding aircraft, the controller outputs an electronic signal to the visual displays.
The visual displays, comprise a plurality of ground-based runway status lights, and an auxiliary display located in the control tower. Moreover, taxiway lights may be provided in locations where each taxiway crosses a runway. The visual displays preferably have three distinct colors, such as red, yellow (amber) and green. Upon receiving the electronic signal from the controller, the runway status lights and the visual display sends a visual signal, in the same manner as a traffic light, that alerts the ground pilots and airport controllers of the calculated optimum takeoff window. Accordingly, the airport control system is advantageous over conventional automated systems since these systems merely inform the aircraft pilot when to xe2x80x9cstopxe2x80x9d or halt the aircraft, while the runway status lights in accordance with the present invention alerts the aircraft pilot when to xe2x80x9cstopxe2x80x9d or halt the aircraft in addition to alerting the pilot when to xe2x80x9cgoxe2x80x9d or proceed on the taxiway. Consequently, the xe2x80x9cgoxe2x80x9d instruction is as important in achieving maximum airport capacity as the xe2x80x9cstopxe2x80x9d instruction is to increase airport safety. Without advising the pilots of both instructions, either airport safety or airport capacity will suffer.
At the same time, the present invention acknowledges the need to present similar information to the tower controller who must retain ultimate control over issuing aircraft directions. By advising pilots when to halt or proceed down the runway via the runway status lights, the pilot can expect a quicker reaction to the desired action. In addition, the use of the runway status lights, in combination with the visual displays in the control tower, provides a system that obviates the disadvantages of conventional radio communications system currently used in airports.
Moreover, the runway status lights provides the ground-based pilot information sufficient to enable him to initiate a takeoff exactly as calculated by the system, and thereby ensure a safe takeoff (i.e., no potential conflict with other landings or takeoffs) and at maximum capacity (i.e., minimum intervals between other aircraft). More particularly, the runway status lights are of a countdown-type in order to provide the pilots awaiting takeoff with information concerning when to expect a takeoff clearance as measured in seconds. For example, the runway status lights indicates using a solid yellow light that a specific takeoff clearance is expected to occur within a first predetermined time and a blinking or flashing yellow light to indicate that the specific takeoff clearance is expected to occur within a second predetermined time interval. A blinking or flashing green light indicates takeoff clearance is expected to occur at a third predetermined time interval, while a solid green light indicates that the aircraft may proceed with takeoff. For the taxiway lights, a red signal indicates that no access to the runway is permitted, a yellow signal indicates clearance to enter or cross the runway is expected within approximately 10 sec, and a green signal indicates authorization or approval is granted to enter or cross the active runway.
Moreover, the system will decide what is the appropriate (i.e., minimum) interval between a takeoff on a first runway and a landing on a second crossing runway and a takeoff on one runway and a landing on the same runway. This information is to be determined by the FAA and the tower controllers and may be varied depending upon environmental factors such as wind, weather, and visibility. The chosen intervals should be no more restrictive than the best controllers now use to separate landings from takeoffs. The system will decide what is the appropriate (i.e., minimum) taxi time to permit an aircraft to cross an active runway, and also decide what is the appropriate (i.e, minimum) interval between initiating the crossing action and the prior takeoff or landing, or subsequent takeoff or landing. The chosen interval should be approximately the same as those used by the best controllers in controlling aircraft.
Tower controllers will be provided with information concerning runway use which parallels the information being given to the pilots. The tower controller will have the option of negating a future aircraft takeoff window instruction to the pilot to either takeoff or enter/cross an active runway since, in all instances, at least a 10 second warning will be given (a flashing light) which will allow the controller with sufficient time to make a determination concerning the reasonableness of the indicated action.
When departure in-trail restrictions are applicable, such information will be provided to the system, which will ensure appropriate intervals between successive departures on the same outbound track to satisfy the in-trail restrictions. While the intrail restriction may be a hard or fixed number, the system may well treat it as a soft or variable number as determined to be reasonable by the tower controllers.